1. Field of the Invention
The present invention relates to a key structure which is applied to a key having a wood part, and a keyboard apparatus including the key structure.
2. Description of the Related Art
Conventionally, key structures are known which function as a key pivotally moved by key depression and for which wood or the like is used, as disclosed in Japanese Utility Model Registration Publication No. 2514485 and Japanese Laid-Open Patent Publication (Kokai) No. 2903959. In such a woody key structure, a woody material is used at least for a so-called “visible part” which is visible from the outside during both performance and non-performance, the key structure presents a woody appearance and hence a high-quality appearance.
In the woody key structure, the wood part is supportedly fixed e.g. using an adhesive to the lower surface of an upper plate member having a depressing surface, or to the upper surface of a key base body as a lower plate member. The support members, such as the upper plate member and the key base body, have elongated shapes corresponding to the shape of the key, and these support members and the wood part form the key structure.
Differently from synthetic resin which can be accurately shaped by molding, wood, which cannot be molded, is formed into a desired shape basically by cutting or machining. For example, to make the width of the key structure equal to a predetermined width set for each key of the keyboard apparatus, it is necessary to cut or machine the left and right sides of the key structure which includes the wood part. In this operation, generally, the key structure is cut for width adjustment using a cutting tool, such as a rotary tool, which is moved in the longitudinal direction along the key structure, so as to make the width of the key structure uniform along the length thereof.
However, the key structure may include a region in the longitudinal direction where no wood part exists, e.g. as in the case where the key structure has a rear end part formed of only resin without any wood part. When the cutting tool moves along such a region of the key structure as the above-mentioned rear end part where only a resin part exists without any wood part, the cutting blade of the cutting tool is brought into contact with a wide region of the resin part. Machining conditions suited to resin parts are different from those suited to wood parts, and therefore the edge of the cutting blade tends to cut undesirably deep into the resin part to cause damage, such as cracking or chipping, to the resin part.
Further, depending on the shape of a bonded part between the wood part and the support member, the rigidity of the key structure itself can be low or the rigidity can vary along the length of the key structure, so that stress can be concentrated on parts low in rigidity, i.e. weak parts, which can cause a deformed or damaged key structure. For example, when an appropriate clearance having a longitudinal component is provided between the wood part and the support member so as to accommodate variations in the longitudinal dimensions of the two parts, the clearance can produce the least rigid part of the key structure. Such a discontinuity in rigidity of the key structure is undesirable since it brings about the reduced rigidity of the key. In spite of these circumstances, there is a constant demand for the reduction of sizes and weights of keys and keyboard apparatuses.